Accurate prediction of the amount of in situ tumor in palpable breast cancers by core needle biopsy: Implications for neoadjuvant therapy

Background: Neoadjuvant chemotherapy facilitates breast conservation in sta ge II breast cancer patients, whose primary tumors are assumed to be invasi ve because they are palpable. However, chemotherapy may not be indicated in the minority of patients whose clinically T2 tumors are completely or pred ominantly in situ. Almost all previous studies of core needle biopsy in bre ast cancer have been concerned with nonpalpable, mammographically detected tumors, and none have evaluated its ability to quantitatively determine the amounts of in situ and invasive disease. Methods: From September, 1992 to December, 1997, core needle biopsy was per formed on all patients presenting to the Kings County Hospital Breast Clini c with palpable breast masses. Carcinoma was present in both core needle bi opsy samples and surgical specimens subsequently obtained from 95 of 99 pat ients. Each specimen was evaluated for tumor type, histologic grade, and th e amounts of in situ and invasive carcinoma it contained, and the results f rom surgical and core needle biopsy specimens from the same patients were t hen compared. Results: The surgical specimens of 14 patients had completely or predominan tly in situ disease. Completely or predominantly invasive disease was prese nt in 67 specimens, and the remaining 14 had significant amounts of both. T he high level of agreement between the amounts of in situ and invasive dise ase in core needle biopsy and surgical specimens is indicated by Pearson an d intraclass correlation coefficients of 0.91 (P < .001 and < .00001, respe ctively). Tumor type was correctly predicted by core needle biopsy in each case. Variables among these patients, including primary tumor size, interva l between biopsy and surgery, or administration of neoadjuvant systemic the rapy, did not alter agreement between core needle biopsy and surgical speci mens. Conclusions: Core needle biopsy can identify palpable breast tumors that ar e predominantly or completely in situ, and, thus, avoid unnecessary neoadju vant chemotherapy. It also can demonstrate that a tumor is predominantly in vasive, but cannot rule out small invasive foci. For that purpose, complete surgical excision of the tumor is required.